RewriteRule ^cat-([0-9]*).html index.php?p=index&cat=$1 [L]
ETC ...

RewriteRule ^cat-([0-9]+).html$ index.php?p=index&cat=$1 [L]
ETC ...

http://www.fire-soft-board.com/fsb/sujet-8547-1html
http://www.fire-soft-board.com/fsb/sujet-8547-1ahtml
http://www.fire-soft-board.com/fsb/sujet-8547-1bhtml
http://www.fire-soft-board.com/fsb/sujet-8547-1\html
http://www.fire-soft-board.com/fsb/sujet-8547-1/html

RewriteEngine On
RewriteBase /
RewriteRule ^cat-([0-9]+)\.html$ index.php?p=index&cat=$1 [L]
RewriteRule ^forum-([0-9]+)-([0-9]+)\.html$ index.php?p=forum&f_id=$1&page=$2 [L]
RewriteRule ^topic-([0-9]+)-([0-9]+)\.html$ index.php?p=topic&t_id=$1&page=$2 [L]
RewriteRule ^profile-([0-9]+)\.html$ index.php?p=userprofile&id=$1 [L]
RewriteRule ^portail\.html$ index.php?p=portail [L]
RewriteRule ^topic-author-([0-9]+)\.html$ index.php?p=search&mode=author_topic&id=$1 [L]
RewriteRule ^topic-author-([0-9]+)-([0-9]+)\.html$ index.php?p=search&mode=author_topic&id=$1&page=$2 [L]
RewriteRule ^author-([0-9]+).html$ index.php?p=search&mode=author&id=$1 [L]
RewriteRule ^author-([0-9]+)-([0-9]+)\.html$ index.php?p=search&mode=author&id=$1&page=$2 [L]